This invention is related to the measurement of the thickness of thin films, such as those grown or deposited in the course of processing a semiconductor wafer to form integrated circuits thereon.
There are numerous processes involving thin films where the thickness of the film must be measured. Usually, it is desired that a new film formed on a substrate have a desired thickness within close tolerances. Other applications involve removal of material from a layer in order to form a thin film having a precise thickness. A major application of thin film technology is found in the manufacturing of integrated circuits, both in silicon semiconductor and gallium arsenide based technology. A typical process of forming integrated circuits on a substrate wafer involves the formation of many films and the removal of films, where it is necessary to know at least when the endpoint of the film formation or removal step has been completed. It is also desirable to be able to monitor and control the process in real time by a technique that does not itself interfere with the process.
Therefore, it is a primary object of the present invention to provide such a film monitoring process having a general utility in various processes where thin films are utilized, such as in the manufacture of integrated circuits.
It is another object of the present invention to provide a technique for measuring the thickness of very thin films with a high degree of accuracy and high resolution.